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use crate::ChannelEvent;
use dashmap::DashSet;
use std::sync::Arc;

/**
A data structure that tracks what topics a given client is subscribed to.
*/
#[derive(Clone, Default, Debug)]
pub struct Subscriptions(Arc<DashSet<String>>);
impl Subscriptions {
    /**
    adds the provided topic to the set of subscriptions. please note
    that this is case sensitive .
     */
    pub fn join(&self, topic: String) {
        self.0.insert(topic);
    }

    /**
    removes the provided topic to the set of subscriptions, if it was
    previously subscribed. please note that this is case sensitive
     */
    pub fn leave(&self, topic: &str) {
        self.0.remove(topic);
    }

    /**
    predicate function to determine if a ChannelEvent is applicable to
    a given user. `phx_join` and `phx_leave` are always applicable, as
    are any topics that are subscribed to by this client (as an exact
    match).
     */
    pub fn subscribes(&self, event: &ChannelEvent) -> bool {
        event.is_system_event() || self.0.contains(event.topic())
    }
}